A metal oxide semiconductor (MOS) image sensor includes a pixel unit formed on a semiconductor substrate and including a photoelectric conversion unit for converting incident light into an electric signal and a peripheral circuit unit formed at the periphery of the pixel unit. In a solid-state imaging device such as the MOS image sensor, a demand for the peripheral circuit unit to operate at a high speed has been increasing in recent years. In accordance with this trend, a demand for the miniaturization of a MOS transistor included in the peripheral circuit unit has been increasing (e.g., Patent Literature 1 (PTL 1)).
Moreover, Patent Literature 2 (PTL 2) suggests a new image sensor (stacked image sensor) including a photoelectric conversion element (a photoelectric conversion film) formed on wiring rather than on a silicon substrate.